Currently lets say I have my outbound email environment send out this domain mail.xxx.com. but we have 3 separate smtp server with different IP addresses pointing to said domain.

So when you do a reverse look each IP resolve back to mail.xxx.com.

Right now we seem to have a problem where certain mailserver would deny our mail because of inconsistent reverse lookup.

I take it this not a practice that is typically done. But this how I found it setup. Can someone confirm this is bad and how I should resolve it. I have an idea but would like to get other input to see if I am corrrect. Thanks for the help in advance.

There is no issue if you have 3 IP addresses with PTRs set to the same host name.
Bad would be having the same IP with multiple host names. (Similar to round-robin forward DNS).
The way you described your setup, there should be no issue.

Basically as long as you have rDNS, and if possible, matching the forward DNS, you are good.

Oh ok I understand a little more now. I would set like smtp1.domain.com, smtp2, etc for the SMTP servers individually. Set the PTR to match. Make sure you have forward A records matching and name the IPs in a SPF record giving the IPs authority to send for your domain.
Sounds like the complaint is bases on different IPs presenting themselves as the same rDNS. I've never seen a complaint like that, but many large providers are getting more and more anal retentive. :)

No there shouldn't really be any outage unless its a server already denying, then you would just pair for your TTLs to expire. Changing the DNS should only make things better, especially if you add an SPF Immediately.

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